Systems and methods for controlling on-board generation and use of hydrogen fuel mixtures

ABSTRACT

This is a system for generating hydrogen on-board the vehicle from compressed natural gas (CNG) in select ratios to create hydrogen-enriched CNG (HCNG) fuel for use in internal combustion engines. The on-board generation of hydrogen is comprised of a reforming system of CNG fuel with direct contact with exhaust gases. The reforming system controls for production of HCNG fuel mixtures is based on specific engine operating conditions. The vehicle&#39;s engine controls and operating parameters are modified for combustion of selective ratios of HCNG fuel mixtures throughout engine operating cycle. The reforming system controls and engine controls modifications are also used to minimize combustion emissions and optimize engine performance.

PRIORITY DATA

The present application is a continuation of U.S. Pat. No. 14/477,727,filed Sep. 4, 2014, which is based on and claims the benefit under 35U.S.C. § 119 of U.S. Provisional Application No. 61/873,491, filed Sep.4, 2013.

TECHNICAL FIELD

This invention relates generally to the on-board vehicle generation ofhydrogen-enriched natural gas fuel for use as an alternative fuel, andparticularly to integrated control systems for generation of hydrogenfuel mixtures and use in internal combustion engines.

BACKGROUND

Hydrogen-enriched Compressed Natural Gas (HCNG) is a clean alternativefuel that combines the advantages of natural gas and hydrogen fuels formotor vehicle engines. Hydrogen enrichment improves the low burningvelocity and poor combustion stability of Natural Gas fueled engines.Natural Gas fuel has generated much interest as an alternative fuel dueto its potential for low particulate and hydrocarbon emissions. HCNGfuels provide advantages over Natural Gas by increasing efficiencies,power output, and further reducing emission through engine controlsmodifications.

Hydrogen is the most abundant element in the universe and is consideredby the scientific community as the ideal alternative fuel. However, thepresent lack of hydrogen infrastructure, including production,distribution, and storage, and the high capital cost of developing thatinfrastructure has made the widespread use of hydrogen fuel economicallyunfeasible.

An effective solution for overcoming the structural barriers to the useof HCNG fuel is the on-board generation of hydrogen in motor vehiclesthrough a natural gas reforming system utilizing engine exhaust gases.The utility of this system overcomes the costs, inefficiencies, andsafety hazards associated with the production, distribution, and storageof hydrogen fuels.

Natural gas expressed in mole fraction is typically 95% methane. Othercomponents include less than 2% ethane, propane, and less than 1% inertgases such as carbon dioxide and nitrogen. Raw natural gas requiresprocessing to remove impurities, including water, to meet industryspecifications for marketable natural gas.

Hydrogen is produced by a number of different processes including watersplitting, electrolysis, and separation from industrial waste streams.Hydrogen can also be produced through reforming natural gas. A reformeris a form of fuel processor that converts hydrocarbon fuels includingmethane, propane and natural gas into hydrogen. The majority ofcommercially available hydrogen is generated through steam-methanereforming. Typically, a multi-step process is used to produce a highpurity hydrogen gas stream, which can be used for a variety of purposesincluding mixture with other gases to produce an alternative fuel.

The most common form of reforming employs the use of steam (H₂O) and ahydrocarbon fuel. The hydrocarbon fuel is reacted in a heated reactiontube containing steam (H₂O) and at least one other catalyst. The primaryderived reaction in the steam reformer is an Equilibrium Reaction (1) asindicated:CH₄+H₂O

CO+3 H₂  (I)

As Equilibrium Reaction (I) moves to the right 2 moles of gas areconverted to 4 moles of gas. This causes the reaction to be highlyendothermic (−198 kJ/mol) and demonstrates pressure sensitivity (LeChatelier's Principle) as hydrogen production is enhanced at lowerpressures.

All four of the substances in Equilibrium Reaction (I) exist in thereformer as a gas mixture with excess steam (H₂O). In addition to theprimary products of CO and H₂, a secondary Equilibrium Reaction (II)occurs:CO+H₂O

CO₂+H₂  (II)

Equilibrium Reaction (II) is the Water Gas Shift Reaction. The reformercontains five gases in varying concentrations according to theequilibrium constants for Reactions (I) and (II). These equilibriumconstants are temperature sensitive (see FIG. 1).

A separate Shift Reactor operates at a lower temperature to enhanceEquilibrium Reaction (II). The overall objective of the reforming andshift reactions is to maximize hydrogen production.

Four other gases are present in varying concentrations and areimpurities that must be removed in order to produce high purity hydrogen(H₂). The passage of methane (CH₄) through the process withoutundergoing reaction is known as “methane slip”. For most hydrogenapplications methane slip and carbon monoxide (CO) are impurities thatmust be removed. Fuel cell hydrogen requires a level of purity thatdictates additional steps to remove relatively inert methane (CH₄) andcarbon dioxide (CO₂), and carbon monoxide (CO). Otherwise, hydrogenimpurities degrade fuel cell performance and catalyst life. The gasstream exiting the shift reactor also contains water vapor (H₂O) whichmust be removed by a condenser before further purification measures areapplied.

In order to make high purity hydrogen (H₂), a final pressure swingadsorption (PSA) process may be performed. The PSA process involves ahigh pressure adsorption of impurities from the hydrogen (H₂) onto afixed bed of adsorbents. The impurities are subsequently desorbed at lowpressure into an off-gas stream, thereby producing an extremely purehydrogen gas (H₂). For example, product purities in excess of 99.999%(H₂) by volume percentage can be achieved. The off-gas stream, whichincludes carbon dioxide (CO₂), carbon monoxide (CO), methane (CH₄) plussmall amounts of water vapor and hydrogen (H₂), is returned to theprocess as supplemental fuel.

A process for producing hydrogen through steam-methane reforming isshown in FIG. 2. In Step 1 a hydrogen-rich gas stream is produced byinjecting methane (CH₄) and steam (H₂O) into a reformer where it isreacts in the presence of a catalyst.

Step 2 moves the hydrogen-rich gas stream through a shift reactor wherecarbon monoxide (CO) reacts with steam to produce additional hydrogen.Both Steps 1 and 2 are endothermic reactions requiring a heat source.Step 3 is a condensing step to remove most of the water vapor (H₂O) fromthe hydrogen-rich gas stream. Step 4 is compression step where thehydrogen-rich gas is compressed to a specified pressure. Step 5 is thePSA step to remove impurities from the hydrogen-rich gas stream. Theimpurities include carbon dioxide (CO₂), carbon monoxide (CO), methane(CH₄), and residual water vapor (H₂O) which, in addition to smallquantities of hydrogen (H₂), are recycled back to the boiler and/orauxiliary burners (not shown). It is also general practice to recoverwaste heat throughout the process with various heat exchangers (notshown).

The traditional methods of producing high purity hydrogen gas hasrequired significant capital investment in compressor and PSA columns aswell as operating expenses to supply electric power for the compressor.The PSA apparatus is comprised of vessels and valves connected andseparated through conduits that have been difficult to reduce in size.

SUMMARY

This disclosure is directed to a system and synchronized process for theon-board production of calibrated quantities of hydrogen for theenrichment of natural gas for use as an alternative fuel with reducedcosts and increased energy efficiency relative to conventional hydrogenproduction systems. Unlike present processes this system's performanceis not affected negatively by impurities in the hydrogen.

A system and a synchronized process are provided for integrating theproduction of selective ratios of Hydrogen-enriched CNG (HCNG) fuelon-board the vehicle through a reforming system and engine controlsmodifications for the use of HCNG fuel mixtures throughout the engineoperating cycle. The reforming system is comprised of reformer controlsand reforming processes to produce selective ratios of Hydrogen in HCNG.Engine parameter and controls modifications are to include excess airratio for lean fuel combustion process and ignition timing adjustmentsto reduce emissions and increase engine efficiencies and power output.

The reforming system includes a reformer configured to react CNG withengine exhaust gas components to produce an impure hydrogen rich gasstream. The exhaust gas flows are controlled by the reforming system tobe extracted after the exhaust manifold to supply the reformer with therequired steam and temperatures for direct contact with CNG in thereforming process. The first process in the reforming system is aPartial Oxidation (POX) reforming of CNG with excess air present in theexhaust gas supply to the reforming system. This requirement is afunction of the excess air ratio nature of combustion. The partialoxidation reaction occurs when a sub-stoichiometric fuel-air mixture ispartially combusted in the reformer, creating a hydrogen-rich synthesisgas or syngas. The chemical reaction of POX for methane takes thefollowing form:CH₄+½O₂→CO+2H₂  (III)

The second step in the reforming process is the steam reforming of CNGfuel to produce 3 moles Hydrogen (H₂) for every one mole of methanesupplied to the reformer. The reforming system controls monitor engineoperating parameters to configure exhaust gas and CNG flows to the POXand steam reformers. The operating temperature of the steam reformerranges from 700° C. to 800° C. with the required heat provided byexhaust gas temperatures and POX exothermic reactions.

The presence of carbon dioxide (CO₂) in exhaust gases at hightemperatures provides an additional opportunity for a methane reformingprocess known as the “carbon dioxide reforming of methane.” This processemploys a different catalyst than is used in steam reforming. Thechemical reaction is represented by:CO₂+CH₄→2H₂+2CO  (IV)

Additional Hydrogen can be recovered at lower temperatures through watergas shift reactions (CO+H₂O

CO₂+H₂ Reaction II). At least one water gas shift reaction is requiredat 350° C. to maximize hydrogen generation and reduce carbon monoxide(CO) concentration to a few percentage points. A second water gas shiftreaction at lower temperatures will further reduce carbon monoxide andproduce more hydrogen.

After the reforming system produces hydrogen, the reformed gas stream ispremixed with the CNG main fuel supply to produce a selective hydrogenratio HCNG fuel for engine combustion. The ideal ratios of Hydrogen inHCNG fuel ranges from 20% to 30% (by weight) for optimal engineoperation. Selective Hydrogen ratios are obtained from the reformingsystem controls by manipulating the CNG and exhaust gas flows to thereforming system, and controlling each stage in the reforming reactionsgeneration of hydrogen gas.

The reforming system controls and engine control units are interactiveto determine precise engine operating conditions with HCNG. Datatransmission and communication between the two control systems providesthe hydrogen ratios in HCNG and engine control parameters for optimizedcombustion. Efficiency gains of up to 31% are achievable with CNGreformation based on enthalpy gains through hydrogen generation.Emissions are reduced (up to 90% reduction in NOx emissions) whenexhaust gas is used in direct contact reforming of CNG. Engine heatlosses are employed to provide the temperatures necessary in thereforming system. The steam supply required for the reforming system isprovided by the exhaust gas compounds, bypassing the need for a separateheated water supply. Carbon dioxide in the exhaust gases is used forfurther methane reforming and production of more Hydrogen, with anadditional reduction of greenhouse gases.

Engine controls modifications include adjustments to air-fuel ratios andignition timing. HCNG fuel mixtures require air-fuel ratio rangesbetween 1.3 and 1.8 for optimal combustion performance. The ignitiontiming adjustments along with air-fuel ratios are the main engineparameters contributing to both emission reductions and engineperformance. These adjustments are based on engine operating conditionsand the Hydrogen ratio in HCNG.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in the referenced figures of thedrawings. It is intended that the embodiments and the figures disclosedherein are to be considered illustrative rather than limiting.

FIG. 1 is the equilibrium concentration graph for a steam methanereformer, illustrating the concentrations of CH₄, CO₂, CO, H₂O and H₂ inmoles versus temperature in degrees Celsius (C) and at initialconditions CH₄ is 1 mole for this illustration.

FIG. 2 is a block diagram of a process flow for steam-methane reformingin a prior art

FIG. 3 is a schematic view of a system on-board a vehicle for producingHCNG

FIG. 4 is a block diagram illustrating a process flow in an on-boardvehicle system for producing a hydrogen-enriched natural gas fuel

FIG. 5 is a block diagram illustrating the interaction and connectivitybetween the Reforming System Controls and Engine Controls Unit and theReformers and Reactors of the System

FIG. 6 is a block diagram illustrating steps in producing HCNG on-boarda vehicle

DETAILED DESCRIPTION

The following definitions are used in the present disclosure.

-   -   CNG means compressed natural gas;    -   HCNG means Hydrogen-enriched compressed natural gas;    -   CH₄ is the chemical composition of methane, the main component        of natural gas;    -   POX means Partial Oxidation process in methane reforming as        described by reaction III;    -   Hydrogen Ratio in HCNG refers to weight and not volume.

FIG. 3 is a schematic view of an on-board vehicle system for producingHCNG. Engine exhaust gases are used for the reforming process as mostreactions in these systems are highly endothermic and require hightemperatures for the conversion of CH₄ to hydrogen. CNG and HCNGcombustion exhaust gases contain the water vapor or steam necessary forthe reforming of methane which eliminates the need for dedicated watersupply tanks and heat exchangers for steam production. Not only doesthis decrease vehicle weight and deliver energy cost savings, but therecirculation of exhaust gases through the reforming system furtherreduces engine emissions.

The first step in the on-board vehicle methane reforming process is POXreforming of CNG due to the excess air present in exhaust gases. HCNGrequires excess air fuel ratios in the combustion process. POX reactionsare exothermic and provide additional heat to the reforming system. Thereforming controls system responds to engine operating conditions andinputs from the engine controls unit to determine the both the amount ofexhaust gases to be extracted and the input quantity of methane for thePOX reactions. The resulting POX reaction products are injected into theCNG reforming system. The CNG is reformed in both a steam reformer and acarbon dioxide reformer at high temperatures in presence of catalysts togenerate a hydrogen-rich gas stream. Both reforming reactions are highlyendothermic, requiring heat and high temperatures, which is supplied byboth POX exothermic reactions and exhaust gases. The hydrogen-rich gasstream is then treated in a Water Gas Shift reactor (WGS) with acatalyst to reduce carbon monoxide (CO) concentrations and generateadditional hydrogen. A second WGS reactor may be implemented at lowertemperatures to produce a more pure hydrogen gas stream. The next stepis mixing the hydrogen-rich gas stream with CNG to generate HCNG fuelfor engine combustion. The ratios of hydrogen in HCNG fuel arecalibrated by the reforming system controls based on engine operatingconditions. Also, engine controls unit modifications and adjustments areconfigured for HCNG fuel mixtures.

FIG. 4 illustrates a System (10) for the On-Board Vehicle production ofHCNG as an alternative fuel according to one embodiment of the presentinvention. The following are the named processes or systems that arecomponents of a System (10) as represented in FIG. 4:

12 Motor Vehicle

14 Reforming System Controls

16 Reforming System

18 Engine Controls Unit (ECU)

20 Vehicle Engine

22 POX Reforming Reactor

24 Steam Reformer

26 Carbon Dioxide Reformer

28 Water Gas Shift Reactor 1 (WGS1)

30 Water Gas Shift Reactor 2 (WGS2)

32 HCNG Mixing Apparatus

34 Vehicle Main CNG Fuel Tank

35 Process

36 Control Systems

FIG. 4 depicts a System (10) that includes a Reforming System (16),Reforming Controls (14), and an ECU (18) on-board a Motor Vehicle (12).The Reforming System (16) may include the following components: POXReactor (22), Steam Reformer (24), Carbon Dioxide Reformer (26), WGS1(28), WGS2 (30). The Reforming System (16) produces a hydrogen-rich gasstream that is blended with CNG in a Mixing Apparatus (32) to produce anHCNG fuel supply for a Vehicle Engine (20). A Process (35) is thesynchronized configuration of the Reforming System Controls (14) and ECU(18) for the operation of the Reforming System (12) and Vehicle Engine(20). Reforming System Controls (14) manage production of selectiveratios of hydrogen in HCNG fuel based on engine operating conditions.The weight ratio of hydrogen in HCNG fuel can range from 20% to 30%depending on engine cycle requirements.

The Reforming System (16) is located on-board the Motor Vehicle (12) inFIG. 4. The Reforming System (16) produces a hydrogen-enriched gasstream by methane reforming in the following sequence of processes: POXReforming Reactor (22), Steam Reformer (24), Carbon Dioxide Reformer(26), WGS1 (28), and WGS2 (30). The gas flow inputs to the ReformingSystem (16) are methane in the form of CNG from the Vehicle Main CNGFuel Tank (34) and exhaust gases from the engine combustion process. TheReforming System (16) controls CNG flows and the amount of exhaust gasextracted for use in powering the vehicle 12. The calibrated extractionof exhaust gas supplies the required amounts of steam and carbon dioxidein methane Reformers (24) and (26). Prior to Reformers (24) and (26) theexhaust gases react with methane in the POX Reforming Reactor (22) basedon the amount of excess air fuel ratio in the combustor process. Thecombustor operation with HCNG, in preferred embodiments, is bestoptimized for emissions and performance with excess air fuel ratios inthe 1.3 to 1.8 range. To use exhaust gases in direct contact withmethane in Reformers (24), (26), (28), and (30) the concentration ofoxygen is minimized by POX Reforming Reactor (22) Reaction III:CH₄+½O₂→CO+2H₂  (III)

Reaction III generates 2 moles of hydrogen for every 1 mole of CH₄supplied to the POX Reforming Reactor (22). The data interchange betweenthe ECU (18) and the Reforming System Controls (14) determines exhaustgas and CNG flows required for the POX Reforming Reactor (22) operation.The POX Reforming Reactor (22) operates in sub-stoichiometric conditionsand supplies additional heat or energy input for endothermic reactionsin Reformers (24), (26), (28), and (30). The hydrogen generation fromthe POX Reforming Reactor (22) contributes a smaller H₂ ratio to HCNGfuel; most of the hydrogen generated by the System (10) occurs in theother Reforming Reactions of components (24), (26), (28), and (30).

The Reforming System (16) depicted in FIG. 4 includes the Steam Reformer(24) configured to generate hydrogen through reaction of methane withwater vapor as shown in Reaction I:CH₄+H₂O→CO+3 H₂  (I)

Reactions in Steam Reformer (24) occur in the presence of catalysts,such as nickel-based catalysts, operating in a temperature range between650° C. and 900° C. Water vapor in exhaust gases supply the steamrequired for the Steam Reformer (24). Direct contact of exhaust gaseswith methane in Steam Reformer (24) provides needed temperature, heatand energy for the reactions with the added benefit of not damaging thecatalysts. The direct contact method construct also eliminates the needfor installing a heat exchanger in the on-board System (10). The SteamReformer (24) contains catalysts in reaction tubes to maximize contactof reactive gases with catalyst surfaces. The flow of both exhaust gasesand CNG to the Steam Reformer (24) is monitored and controlled by theReforming System Controls (14). Note that the catalysts are not limitedto the aforementioned example and one skilled in the art will recognizethis fact.

The Reforming System (16) depicted in FIG. 4 includes the Carbon DioxideReformer (26) configured to generate hydrogen through reaction ofmethane with carbon dioxide as shown in Reaction IV:CO₂+CH₄→2H₂+2CO  (IV)

Reactions in Carbon Dioxide Reformer (26) occur in the presence ofcatalysts, such as rhodium and iron-based catalysts, operating in atemperature range between 700° C. to 800° C. (Note that the catalystsare not limited to the aforementioned example and one skilled in the artwill recognize this fact.) Exhaust gases supply the CO₂ required for theCarbon Dioxide Reformer (26). Direct contact of exhaust gases with CH₄in Carbon Dioxide Reformer (26) provides needed temperature, heat andenergy for the reactions with the added benefit of not damaging thecatalysts. This direct contact method also eliminates the need forinstalling a heat exchanger in the System (10). The Carbon DioxideReformer (26) contains catalysts in reaction tubes to maximize contactof reactive gases with catalyst surfaces. The flow of both exhaust gasesand CNG to the Carbon Dioxide Reformer (26) is monitored and controlledby the Reforming System Controls (14).

Reactions I and IV demonstrate that 5 moles of hydrogen is generated forevery 2 moles of CH₄ input to Reformers (24) and (26). Water Gas Shiftreactions in WGS1 (28) and WGS2 (30) provide one additional mole of H₂for hydrogen enrichment of CNG fuel as shown in Reaction II:CO+H₂O→CO₂+H₂  (II)

The WGS1 (28) operates between 350° C. and 420° C. and employscatalysts, such as iron oxide-based catalysts, to convert CO formed inReactions I and IV to hydrogen. CO concentrations in the ReformingSystem (16) hydrogen-rich gas stream exiting WGS1 (28) are reduced toless than 4%. Note that the catalysts are not limited to theaforementioned example and one skilled in the art will recognize thisfact.

The Reforming System (16) may employ a second WGS2 to further reduce COconcentrations in the gas stream. Because it operates at temperaturesbelow 200° C., characterized by costly catalysts and slow reactionkinetics, WGS (30) should be used in systems requiring purer forms ofhydrogen.

Fuel Cell applications require stringently pure hydrogen for operation.In the Prior Art, the removal of impurities from a hydrogen-rich gasstream requires a significant investment in capital assets, operatingexpense, high energy consumption. Unlike Fuel Cell systems, theimpurities in HCNG fuel hydrogen do not have a negative effect on theoperation or performance of the Vehicle Engine (20) in the System (10).

A hydrogen-rich gas stream from the Reforming System (16) is blendedwith CNG fuel in the HCNG Mixing Apparatus (32) to produce HCNG fuel forVehicle Engine (20) combustion as shown in FIG. 4. Hydrogen forenrichment of CNG to create HCNG is generated by the System (10)on-demand at no additional cost to the Motor Vehicle (12) operator. ThisJust-in-Time process eliminates the cost and inefficiencies associatedpurchasing and storing hydrogen for use as a motor vehicle fuel bothon-board the vehicle and upstream throughout the hydrogen fuel supplychain. Because hydrogen is generated on-demand in the System (10), MotorVehicles (12) do not require the weight, space consumption, operatinginefficiencies, and additional costs associated with existing hydrogenfuel systems.

The Control Systems (36) for the System 10) is depicted in FIG. 5. TheControl Systems (36) consists of two control modules: the ReformingSystem Controls (14) and the Engine Controls Unit or ECU (18). TheReforming System Controls (14) monitor and manage the on-board vehiclegeneration of hydrogen by producing selective H₂ ratios in HCNG fuelmixtures for the System (10).

FIG. 5 illustrates how the Reforming System Controls (14) and ECU (18)are connected by Data Link (40) to ensure the synchronized operation ofthe Reforming System (16) and Vehicle Engine (20). The ECU (18) collectsoperational and parametric data from the Vehicle Engine (20) thentransmits that data to the Reforming System Controls (14). This dataexchange calibrates the amount of engine exhaust gases to be extractedfor the Reforming System (16) operation. Reforming System Controls (14)manage the flow rates of CNG and exhaust gas to the Reforming System(16). The CNG flow rate to POX (22) is based on excess air in theexhaust gas composition. The ECU (18) communicates air-fuel ratio fromthe combustion process to the Reforming System Controls (14) todetermine the CNG flow rate to POX (22) for reaction with oxygen.

The Reforming System Controls (14) determine the flow of CNG toReformers (22), (24), and (26) to produce hydrogen in selectivequantities. This is synchronized with the flow of exhaust gas to theReforming System (16) to supply the correct amount of steam and CO₂required for the generation of hydrogen. The ECU (18) transmits VehicleEngine (20) operating data, including fuel flow rate and combustorefficiency, to the Reformer System Controls (14) which determines thespecific amount of H₂O and CO₂ in the Vehicle Engine (20) exhaust gas.

The Reforming System Controls (14) monitor and manage the flow rate ofthe hydrogen-rich gas stream and CNG to the Mixing Apparatus (32) toproduce selective hydrogen ratios in HCNG fuel. The hydrogen ratiosrange from 20% to 30% of the HCNG fuel mixtures. The H₂ ratio is basedon engine operating data for optimal performance and emission controls.The Reforming System Controls (14) communicates the H₂ ratio to the ECU(18) for setting combustor operating parameters.

The ECU (18) is configured for HCNG fuel to increase efficiency, poweroutput and to reduce emissions in the Vehicle Engine (20). The ECU (18)monitors and manages Vehicle Engine (20) parameters for combustionprocess for HCNG fuel throughout the Vehicle Engine's (20) completeoperating cycle. A principle advantage of HCNG fuel is combustion withexcess air fuel ratios. The addition of hydrogen raises CNG's lean burnlimit which reduces Vehicle Engine (20) emissions, especially NOx and CO, and decreases fuel consumption. The lean burn limit of HCNG isincreased because of the faster burn speed, flame velocity, and laminarburn properties of hydrogen . The ECU (18) can vary the excess air fuelratio from 1.3 to 1.8 based on the Vehicle Engine's (30) operating dataand the HCNG fuel's H₂ ratio.

HCNG fuel combustion with excess air fuel ratios requires ECU (18) toadjust ignition timing parameters based on operating conditions and H₂ratio. The ignition timing adjustments are optimized along with H₂ratios and excess air fuel ratios to increase engine efficiency, poweroutput and to reduce exhaust emissions. Ignition timing configuration inECU (18) is significant to engine (20) operation with HCNG fuel in orderto avoid engine knock and increased NOx emissions.

FIG. 6 is a block diagram illustrating the steps of the System (10) forproducing HCNG on-board a Motor Vehicle (12). These steps may varydepending on the application. For example, some applications may notrequire the WGS2 step which delivers a higher level of hydrogen purity.

The steps of the method in FIG. 6 include:

-   -   Supply Compressed Natural Gas (CNG) to the Reforming System (16)        in FIG. 4;    -   Supply Vehicle Engine (20) exhaust gas to the Reforming System        (16) in FIG. 4;    -   Reacting CNG with exhaust gas in the POX Reforming Reactor (22);    -   Reacting Steam from POX reaction products with CNG in a Steam        Reformer (24) to produce a hydrogen-rich gas stream;    -   Reacting CO₂ from POX reaction products with CNG in a Carbon        Dioxide Reformer (26) to produce a hydrogen-rich gas stream;    -   Reacting Steam from POX reaction products with hydrogen-rich gas        streams in Water Gas Shift Reactor 1 (28) to remove carbon        monoxide (CO) and produce additional hydrogen;    -   Reacting Steam from POX reaction products with hydrogen-rich gas        streams in Water Gas Shift Reactor 2 (30) to further purify        hydrogen;    -   Mixing and blending the hydrogen-rich gas stream with CNG in the        HCNG Mixing Apparatus (32) to produce HCNG alternative fuel.

While the invention has been described with reference to certainpreferred embodiments, as will be apparent to those skilled in the art,certain changes and modifications can be made without departing from thescope of the invention. Moreover, the foregoing examples of the relatedart and limitations related therewith are intended to be illustrativeand not exclusive. Other limitations of the related art will becomeapparent to those of skill in the art upon a reading of thespecification and a study of the drawings. Similarly, the embodiments ofthe present invention and aspects thereof are described and illustratedin conjunction with a system and synchronized process, which are meantto be exemplary and illustrative, not limiting in scope.

In the present disclosure, certain details are set forth in conjunctionwith the described embodiments of the present invention to provide asufficient understanding of the invention. One skilled in the art willappreciate, however, that the invention may be practiced without theseparticular details. Furthermore, one skilled in the art will appreciatethat the example embodiments described do not limit the scope of thepresent invention, and will also understand that various modifications,equivalents, and combinations of the disclosed embodiments andcomponents of such embodiments are within the scope of the presentinvention. Embodiments including fewer than all the components of any ofthe respective described embodiments may also be within the scope of thepresent invention although not expressly described in detail. Finally,the operation of well-known components and/or processes has not beenshown or described in detail below to avoid unnecessarily obscuring thepresent invention.

What is claimed is:
 1. An engine system, comprising: an on-board vehiclesystem configured to operate on-board a vehicle, the on-board vehiclesystem including: a combustion system configured to combust natural gasto generate energy and exhaust gas; a pre-reforming system configured toreceive unreformed natural gas and coupled to the combustion system toreceive at least a portion of the exhaust gas, the pre-reforming systemconfigured to generate a partial oxidation reaction between theunreformed natural gas and the exhaust gas to generate partial oxidationreaction products; a reforming system including a steam reformer, acarbon dioxide reformer, and a first water-gas-shift reformer, thereforming system coupled to the pre-reforming system and configured toreform the partial oxidation reaction products to produce reformednatural gas; a mixing system coupled to the reforming system andconfigured to mix reformed natural gas and unreformed natural gas thatis provided as the natural gas to the combustion system; and a reformingcontrol system coupled to the pre-reforming system and configured tocontrol the supply of the exhaust gas to the pre-forming system so thesupplied exhaust gas has a first ratio with the unreformed natural gasbased on a first operating condition and is configured to control thesupply of the exhaust gas so the supplied exhaust gas has a second ratiowith the unreformed natural gas based on a second operating condition.2. The engine system of claim 1, wherein the reforming control system isfurther configured to control an amount of the unreformed natural gasdelivered to the pre-reforming system as a ratio with the generatedexhaust gas.
 3. The engine system of claim 1 further comprising anengine control unit, and wherein the reforming system is integrated withthe engine control unit.
 4. The engine system of claim 3, wherein thereforming control system is configured to extract the exhaust gassesfrom the combustion system based on inputs from the engine control unitfor required amounts of steam and carbon dioxide for generation ofhydrogen.